Shock absorbing linkage mechanism



Nov. 8, 1960 s. KAPLAN SHOCK ABSORBING LINKAGE MECHANISM 2 Sheets-Sheet1 Filed Dec. 23, 1957 INVENTOR Louss G. KAPLAN ATTY.

Nov. 8, 1960 L. G. KAPLAN 2, 5 11 SHOCK ABSORBING LINKAGE MECHANISMFiled Dec. 23, 1957 2 Sheets-Sheet 2 14o -s" I24 72 1:: l I l.

i I I lea 27L120 86 L as INVENTOR I I Louis G. KAPLAN A'r'rv.

United States PatentOfiice 2,959,411 Patented Nov. 8, 1960 SHOCKABSORBING LINKAGE MECHANISM Louis G. Kaplan, Evanston, Ill., assiguor toCullen- Friestedt Company, Chicago, 111., a corporation of IllinoisFiled Dec. 23, 1957, Ser. No. 704,385

1 Claim. (Cl. 267-71) The present invention relates to lifters for usein handling and moving or transporting metallic sheets and like articlesfrom place to place. The invention is particularly concerned withlitters of the type which are adapted to be hoisted and moved from oneplace to another by a crane or overhead hoist. A lifter of thischaracter has as its principal components or parts: (1) a supportingelement having means thereon whereby it may be attached to a hook orother connecting device on the operating end of a crane or a hoist withwhich the lifter is to be used; (2) a pair of opposed horizontallyelongated, complemental jaws which are pivotally connected to thesupporting elements so that they are capable of swinging toward and awayfrom each other into and out of engagement with the side margins of thesheets or other articles to be lifted; (3) a reversible electric motorwhich is mounted on the supporting element; and (4) a train of motoractuated gearing which is associated with, and carried by, thesupporting element, operates when driven in one direction to shift thejaws apart and when driven in the opposite direction to move the jawstoward each other into gripping relation with the sheets or otherarticles and includes a speed reducing unit operatively connectedbetween the drive shaft of the motor and a horizontal rock shaftpositioned under the supporting element and operatively connectedthrough linkage mechanism to the jaws. A lifter of this character hasbeen shown and described in the United States patent to Hooker No.2,695,809, dated November 30, 1954, and entitled Lifter, and the presentinvention is designed as an improvement over such a lifter construction.

In the above-mentioned patent to Hooker there has been disclosed a lostmotion linkage mechanism which extends between the jaw-actuatingrock-shaft and one of the two cooperating jaws, the lost motionmechanism being provided with a take-up spring which is adapted tobecome compressed when the two jaws are brought into engagement with theside margins of the sheets or other articles which are to be lifted orwhen either jaw is subjected to shock or impact tending to limit itsinward swinging motion. The take-up spring associated with the lostmotion linkage mechanism shown and described in the above-mentionedHooker patent serves normally to take up lost motion in One directiononly and thus the lost motion connection is eflective to assimilateshock only when there is an impact tending to limit the inward swingingmotion of the jaws. In the event of an impact tending to limit theoutward swinging motion of the jaws, the lost motion connection is rigidand thus no protection against shock is oflered to either the speedreducing unit or the electric motor which drives the same. Such shockmay be the result of the jaws becoming wedged between two adjacentobjects during their outward swinging motion, or it may be the result ofinadvertent contact between the outer surface of one of the jaws and anadjacent object, either during outward swinging movement of the jaw orduring transportation of the unloaded lifter assembly by the hoistmechanism from one location to another.

It is among the principal objects of the present invention to provide alifter of the type briefly outlined above and shown in theabove-mentioned patent to Hooker in which the actuating rock-shaft forthe lifter jaws is operatively connected to one of the jaws by one ormore double-acting spring-biased lost motion linkage mechanisms capableof absorbing any sudden shock which may be applied to the lifter jawsfrom the outside or from the inside of the jaw structure during outwardor inward swinging movements of the jaws respectively, and also capableof absorbing shock which may be encountered by the jaws duringtransportation of the lifter when the jaws are empty, whether the shockbe occasioned by an inside or an outside blow on the lifter jaws.

Other objects and advantages of the invention, not at this timeenumerated, will become more readily apparent as the nature of theinvention is better understood.

In the accompanying two sheets of drawings forming a part of thisspecification a preferred embodiment of the invention has been shown.

In these drawings:

Fig. 1 is a fragmentary vertical sectional view taken through a lifterassembly in the vicinity of the power actuated gear driving mechanismtherefor and showing improved linkage mechanism of the present inventionoperatively applied thereto;

Fig. 2 is a side elevational view of a link assembly employed inconnection with the present invention;

Fig. 3 is a sectional View taken substantially along the line 33 of Fig.1;

Fig. 4 is a sectional view similar to Fig. 3 showing the link assemblyin an extended position;

Fig. 5 is a sectional view similar to Figs. 3 and 4 showing the linkassembly in a contracted position;

Fig. 6 is a sectional view taken substantially along the line 6-6 ofFig. 3; and

Fig. 7 is a circuit diagram for the electric motor associated with thelifter and illustrating certain safety features employed in connectionwith the invention.

Referring now to the drawings in detail and in particular to Fig. 1, theimproved linkage mechanism of the present invention is shown as beingoperatively applied to a lifter of the general type shown and describedin the above-mentioned patent to Hooker, No. 2,695,809. Only suchportions of the lifter assembly as are pertinent to the operation of thelinkage mechanism have been illustrated herein and for a detaileddescription of the entire mechanism and its mode of operation, referencemay be had to this patent. The lifter involves in its generalorganization an elongated supporting element 10, a pair of jawassemblies 11 and 12, a reversible electric motor 14, and a power train16 extending between the motor and jaws for conjointly shifting thelatter toward and away from each other in response to operation of themotor.

The supporting element 10 is in the form of a horizontally extendingI-beam having horizontal top and bottom flanges 18 and 19, respectively,connected together by a vertically extending web 20. At suitable spacedpoints along the I-beam 19 there are provided a series of spacedattachment or pivot lugs, only one of which has been disclosed hereinand designated at 22. Each lug 22 has pivotally connected thereto onopposite sides thereof one of the pairs of jaw assemblies 11 and 12,each jaw assembly being attached to the lug by means of a pivot pin 24.The pivot lugs 22 fit between the top and bottom flanges 18 and 19 ofthe supporting element 10 and are welded as at 26 in position thereon.The two jaw assemblies 11 and 12 are substantially identical inconstruction and each is in the form of a composite assembly includingan upper or proximate jaw section 28 and a lower or distal jaw section30 hingedly connected as at 31 to the upper section.

The upper jaw section 28 has its upper end region curvedinwardly and thesection is comprised of a pair of laterally spaced flat metal bars 32and 34 (see also Figs. 3, 4 and 5). The upper ends of the bars 32and 34straddle the pivot lug 22 and the pivot pin 24 extends through the threethicknesses of metal involved. The lower section 30 is in the form of asingle fiat metal bar 36, the upper region of which projects between thebars 32 and 34, with the hinge pin 31 extending through the three metalthicknesses. The extreme upper end region of the bar 36 is in the formof a toothed sector 38 capable of swinging movement between the bars 32'and 34 of the upper jaw section 28 and capable of being locked in anydesired angular position of adjustment by means of a lock bar 40 whichpasses through a pair of slots 44 provided in the bars 32 and 34 andwhich is capable of being selectively received in a series of notches 46formed on the periphery of the sector 38. The lock bar and sectorarrangement just described provides a convenient means whereby theangular position of the lower jaw section 30 may be adjusted relative tothe upper jaw section 28 to decrease or increase the effective span ofthe two jaws to adapt the jaws to articles of varying width. The lowerjaw section 30 of each jaw assembly 11 or 12, as the case may be, arecross connected by means of horizontally extending box-section typemembers 49, the ends of which are welded or otherwise secured fixedly tothe central regions of the flat bars 36. The lower ends of the lower jawsections 30 carry opposed angle bar gripping members 50. The electricmotor 14 by means of which the jaws 11 and 12 are actuated is preferablyof the reversible series wound direct current type. The motor includes acasing 51 having a mounting flange 52 secured by bolts 54 to theunderneath side of the horizontal lower flange 19 of the supportingelement 10. The motor has operatively associated therewith a gearreduction mechanism 56 having an output shaft 58 carrying a pinion 60constituting one element of the previously mentioned power train 16.

The power train 16 which extends between the output shaft 58 of the gearreduction device 56 and the jaws 11 and 12 is comprised of a set ofgearing including the pinion 60 and a linkage mechanism, the latterconstituting one of the important features of the present invention. Thegearing, in addition to the pinion 60, comprises a gear segment 62 whichmeshes with the pinion 60. The gear segment 62 is keyed or otherwisesecured to a rock-shaft 64 suitably mounted in bearings 66 provided on abracket 68 which depends from the underneath side of the flangeassociated with the supporting element 10. Also keyed or otherwisesecured to the rockshaft 64 are a pair of bifurcated crank arms 70 and72 which extend radially outwardly from the rock-shaft 64 generally inopposite directions. The distal end of the crank arm 70 is pivotallyconnected as at 74'to one end of a thrust link 76, the other end of thelink 76 being pivotally connected as at 78 to a medial region of theupper jaw section 28 of the jaw 12. The distal end of the crank arm 72is pivotally connected by, a horizontal pivot pin 80 to one end of aspring biased lost motion link assembly designated in its entirety at82, the other end of the link assembly 82 being pivotally connected by ahorizontal pivot pin 84 to a medial region of the upper jaw section 28of the jaw 11.

The arrangement of parts thus far described, with the exception of thespecific character of the link assembly 82, is purely conventional andno claim is made herein to any novelty associated with the same. For amore detailed description of the motor 14, gear reduction device 56, thespecific mounting means for the motor and its gear reduction device andother mechanism which may be associated with the lifter assembly andwhich is not pertinent to the present invention, reference may be had tothe above-mentioned Hooker patent for a full disclosure of thesedetails. The invention of the present application resides rather in thenovel construction and arrangement of parts associated with the springbiased lost motion link assembly 82 which will now be described indetail and its operation subsequently set forth.

The link assembly 82 involves in its general organization fourrelatively movable parts or assemblies, together with a preloadcompression spring which serves to maintain these assemblies in a normalor intermediate position when the link assembly 82 as a whole is in itsfree state, or when compressional or tensional forces below apredetermined minimum are applied to the ends of the assembly. Thecompression spring by means of which these four parts or assemblies arenormally held in their neutral or inoperative position is designated inits entirety at 86.

The four parts or assemblies set forth above include an inner linkmember 100, an outer encompassing link member 102, a slide member 104,and thrust collar 106. The inner link member is of a composite natureand comprises a cylindrical rod 108, one end of which is threaded as atand is threadedly received in a threaded bore 112 of a socket member114. One end of the socket member 114 is welded as at 116 to a sleeve118 which, in combination with the pivot pin 84, provides the pivotalconnection whereby one end of the link assembly is connected to themembers 32 and 34 of the upper jaw section 28 of the jaw 11. The outerlink member 102 may be in the form of a casting providing a pair ofparallel fiat bar-like arms 120, the right hand ends of which, as viewedin Figs. 2, 3, 4 and 5, are connected together by a sleeve portion 122which surrounds and is slidable on the socket portion 114 of the innerlink member 100. The left hand ends of the bar-like arms are connectedby means of the pivot pin 80 to the bifurcated crank arm 72. The upperand lower edges of the arms 120 are each formed with lugs 124 providingshoulders or abutments 126, the function of which will be set forthpresently.

The slide member 104 is in the form of a relatively thick plate or block(Figs. 3 and 6) having a central opening therethrough, through which therod 108 extends and in which opening it is slidable. The opposite edgesof the plate 104 are notched as at 132 to provide pairs of ears 134which straddle the members or arms 120, respectively, so that the block104 is constrainedto slide longitudinally on these arms. The collar 106surrounds the rod 108 in the immediate vicinity of the socket 114 andthe rod 108 is slidable through the collar for purposes which will alsobe made clear presently.

Still referring to Figs. 2, 3, 4 and 5, the compression spring 86 is ofthe helical variety and, in its free state, is provided with a series ofopen or spaced convolutions to allow for limited compression of thespring endwise in the usual manner of operation of such compressionsprings. The spring 86 surrounds the inner rod 108 and bears at one endagainst one side of the slide block 104 and at its other end against thecollar 106. The length of the compression spring is such that itnormally maintains the collar 106 seated against an internal shoulder136 provided at the juncture between the sleeve portion 122 and the arms120, while at the same time maintaining the slide block 104 against theshoulders 126 afforded by the integral lugs 124 on the arms 120. Theleft hand end ofthe rod 108 has mounted thereon a limit collar 138 whichis anchored in position by a set screw 140 and the distance between thecollar 138 and socket member 114 on the rod 108 is such that, in thenormal position of the parts as shown in Fig. 3, the compression spring86 will, through the medium of the collar 106, force the slide block 104and collar 106 outwardly away from each other in opposite directionswhereupon the collar 106 will bear against the extreme end of the socketmember 114and cause, the entire composite inner member 100 of theassembly 82 to be moved to the right as shown inFig. 3 until suchtime asthe limit collar 138 bears against the slide member 134. The spring 86thus maintains the four relatively movable parts 100, 102, 104 and 106of the assembly in the positions in which they are illustrated in Fig.3, this being the neutral position of the assembly when the same isunder neither compressional nor tensional forces.

In the operation of the link assembly 82, when the rock-shaft 64 isturned in a clockwise direction as viewed in Fig. I, the crank arm 70will force the link 76 to the right, thusswinging the jaw 12 outwardlyabout its pivotal axis 24. At the same time the crank arm 72 will forcethe link assembly 82 to the left thusswinging the jaw 11 outwardly aboutits pivotal axis 24. Conversely, as is obvious, when the rock-shaft 64is turned in a counterclockwise direction, the linkage mechanism will beactuated to draw the jaws 11 and 12 inwardly toward each other.

During outward swinging of the jaws 11 and 12 under the motivatinginfluence of the electric motor 14, operating through the gear reductiondevice 56, output shaft 58 thereof, pinion 60, gear segment 62, crankarms 70 and 72, and links 76 and 82, if the jaws 11 and 12 should becomewedged between two opposed adjacent objects, or if one of them shouldstrike an adjacent massive object, counter-torque will be applied to therock-shaft 64 through the link assembly 82 and such counter-torque, whenapplied to the shaft 64, will tend to compress the link assembly 82. Asshown in Fig. 5, the application of compressional forces to the oppositeends of the link assembly 82 will cause the socket member 114 to slideinwardly through the sleeve portion 122 of the outerlink member 102,thus forcing the collar 106 to the left, as viewed in this figure, andcompressing the spring 86 between the collar 106 and slide memher 104which is held against the shoulders 126 of the integral lugs 124 on theside bars 120. Movement of the socket portion 114 in this manner willcause the rod 108 to be slid to the left through the slide member 104 sothat the limit collar 138 moves away from this slide member. Theeffective length of the link assembly 82 thus becomes shortenedand thespring 86 assimilates the shock which otherwise would be imparted to thepower train 116 leading to the motor 14 where conventional rigid linkconstructions are concerned. When the compressional force on the linkassembly 82 is relieved, the parts will be restored to their neutralposition as shown in Fig. 3.

When internal shock is encountered by the jaws 11 and 12, as, forexample, when the angle bar gripping members 50 engage the side marginsof a stack of sheets or other objects to be lifted during inwardswinging movement of the jaws 11 and 12 under the influence of the motor14, such inward swinging motion of the jaws is immediately arrested andtensional forces are applied to the link assembly 82 tending to expandthe same longitudinally. When this occurs the inner link part 100 willbe moved to the right as viewed in Fig. 4 so that the limit collar 138will force the slide block 104 to the right along the members 120 onwhich it is slidable and the spring 86 will be compressed between thisslide block and the collar 106. The collar 106 will bear against theinternal shoulder 136 and thus receive the end thrust of the spring 86.It will be seen, therefore, that the spring 86 assimilates any shockincident upon interruption of the inward swinging movement of the jaws11 and 12.

In order to reduce the flow of current through the electric motor 14when the movement of the jaws 11 and 12 is interrupted, during outwardswinging movement thereof, as previously outlined, a limit switch 150 ismounted on one of the arms 120 of the outer link member 102. The limitswitch 150 is provided with an actuating finger 154 which is positionedin the path of movement of the collar 138 which'moves to the left relative to the arm as seen in Fig. 3 when the spring 86 is compressed underthe influence of compressional forces acting on the opposite ends of thelink assembly 82. The limit switch has associated therewith a normallyopen pair of contacts 158 (Fig. 7), adapted to, become closed under theinfluence of the actuating finger 154. The circuit connections for thelimit switch 150 will be set forth subsequently.

The reversible electric motor 14 is of the series wound, direct currenttype in which reversal of the direction of current flow through themotor armature will effect reversal of the direction of rotation of themotor shaft, and consequently of the output shaft 58 of the gearreduction mechanism 56. Such selective reversal of the current flowthrough the armature circuit of the motor 14 will control the directionof movement of the lifter jaws 11 and 12. In order to prevent excessivemotor speeds during inward swinging movements of the jaws 11 and 12under the influence of gravitational forces acting upon the jaws, meansare provided whereby full line current will be applied to the armaturecircuit with the current flowing through the circuit in a direction tocause clockwise rotation of the rock-shaft 64 and consequent openingmovement of the jaws 11 and 12. The motor 14 will thus be driven underfull power. However, when the direction of current flow through thearmature circuit is reversed so that the power train 16 is actuated tocause counterclockwise rotation of the rock-shaft 64 to effect closingmovement of the jaws 11 and 12, automatically operable means areprovided for introducing a resistance element into the armature circuitso that the motor will be driven under reduced power. The circuitdiagram of Fig. 7 illustrates schematically the manner in which such aresistance is automatically introduced into the armature circuit of themotor and it also illustrates the manner in which the limit switch 150is capable of interrupting the flow of current through the armaturecircuit. V 7

Referring now to Fig. 7 in detail, full line current may be applied tothe armature circuit of the motor 14 from the positive side of the line,through a reversing switch 160, leads 21, 23, motor 14, leads 25, 27, apair of normally closed contacts 29 associated with a relay magnet M,leads 31,33, 35,-and reversing switch 160 to the negative side of theline. Current flowing through the armature of the motor 14 in thisdirection will move the rockshaft 64 in a clockwise direction so as tocause opening movements of the jaws 11 and 12, as previously described.

When the reversing switch 160 is operated to reverse the direction ofcurrent flow through the armature of the motor 14, a circuit will existfrom the positive side of the line through the reversing switch 160,leads 35, 37, relay magnet M, lead 39, a unidirectional device SR whichmay be in the form of a selenium rectifier, leads 47, 49, 21, andreversing switch 160 to the negative side of the line. Energization ofthe relay magnet M will cause opening of the contacts 29, thusestablishing a circuit extending from the negative side of the line,through the reversing switch 160, leads 35, 33, 51, resistance R, leads53, 25, armature of the motor 14, leads 23, 21 and reversing switch 160to the negative side of the line. The ohmic value of the resistor R maybe selected according to engineering requirements to produce a desiredvoltage drop thereacross and reduce the current flow'through the motorarmature to such an extent that overspeeding of the motor 14 under theinfluence of gravitational forces acting upon the jaws 11 and 12 duringclosing movements thereof will be avoided.

The normally open pair of contacts 158 associated with the previouslydescribed limit switch 150 on one of the arms 124 of the outer linkmember 102 is disposed in shunt relationship with the unidirectionaldevice SR.

Thus, when the actuating finger 154 is engaged by the collar 138 and thecontacts 158 become closed,'the unidirectional device SR will bebypassed and a shunt circuit passing through lead 43, contacts 158, lead45 and'magnet M will be completed, thus opening the contacts 29 andrestoring the circuit through the resistor R and motor armature so as toreduce the power output of the motor 10. Such a condition will obtain,for example, when compressional forces are applied to the ends of thelink assembly 82 due to the lifter jaws becoming wedged between twoadjacent objects during opening of the jaws under full motor power, aspreviously described.

A preferred embodiment of the invention has been shown in the drawingsand described herein, but it should be understood that the invention isnot limited to the specific disclosure made. For example, although inFig. 1 only one of the improved lost motion link assemblies 82 has beenshown in association with the gear segment 62, the assembly beingconnected to the jaw 11, it will be understood that the thrust link 76may be replaced by an assembly such as the lost motion link assembly 82having its opposite ends connected between the gear segment 62 and jaw12. The appended claim should, therefore, be construed as broadly as theprior art will permit.

Having thus described the invention what I claim as new and desire tosecure by Letters Patent is:

A compressible and extensible shock absorber link assembly comprisingfour relatively movable link elements capable of axial shifting movementin opposite directions relative to one another and including a firstelement having means for attaching the same to one of said arms, a firststop shoulder on said first element facing said other arm, a secondelement slidable on said first element, having means for attaching thesame to the other arm, a second stop shoulder on said first elementfacing said one arm, a third element slidable on said firstelementibetween the two stop shoulders on the latter and beingengageable with the first stop shoulder, said second element beingslidable through said third element, a'first stop shoulder on saidsecond element facing said one arm, a fourth element slidable on saidfirst element, interposed between said third element and the second stopshoulder on the first element and engageable with said latter stopshoulder, a second stop shoulder on said second element on the side ofthe third element remote from said other arm, facing the latter arm andengageable with said third 8. element, anda compression springsurrounding said second element and bearing atone end against said thirdelement and hearing at the other endagainst a fourth element, saidspring normally urging said fourth element against said second stopshoulder on the'first element and urging the third element against thesecond stop shoulder on the second element, said first stop shoulder onsaid second element being engageable with the fourth element whencompressional forces are appliedto the link assembly by said attachingmeans to compress said spring against said third element, said secondstop shoulder on the second element being engageable with said thirdelement to compress ,said spring against said fourth element whentensional forces are applied to the link assembly by said attachingmeans, said first element being in the form of a pair of spaced parallelbars connected together at the end thereof adjacent said other arm by anintegral collar portion, said second element being in the form of acylindrical rod slidable through said collar portion, said third elementbeing in the form of a block extending across said barsand havingnotches in the lateral side edges thereof within which said bars areslidable, said block also having a hole therethrough through which saidrod extends and in which it is slidable, said means for attaching saidfirst element to said one arm including a cylindrical socket membercarried by said one arm and having a threaded socket formed therein andin which socket one end of said cylindrical rod is threadedly received.

References Cited in thefile of this patent UNITED STATES PATENTS1,137,145 Krarup Apr. 27, 1915 1,460,771 Stoner July 3, 1923 1,621,011Harvey et al. Mar. 15, 1927 1,705,728 Harvey Mar.'19, 1929 1,717,219Jones June 11, 1929 1,757,164 Blake et al. May 6, 1930 1,837,192 Barrowset'al Dec. 22, 1931 2,360,740 Sturdy Oct. 17, 1944 2,372,214 LoepsingerMar. 27, 1945 2,526,373 LeClair Oct. 17, 1950 2,695,809 Hooker Nov. 30,1954 FOREIGN PATENTS 412,838 France July23, 1910

